Human Activities In Southeast Atlantic Affect Humpback Whale Routes

February 6, 2014

Image Caption: In the waters off the coast of Gabon, a humpback whale lunge-feeds in the near vicinity of an offshore oil platform. In a recently published study in Conservation Biology, scientists have quantified the overlap between humpback whales using Africa's coastal waters and several forms of ocean industries and ocean-based pollution, primarily offshore oil platforms, shipping lanes, and potentially harmful toxicants. Credit: Photo credit: T. Collins/Wildlife Conservation Society.

Swimming off the coast of Africa, humpback whales encounter more than warm waters for mating and bearing young, according to a new study led by the Wildlife Conservation Society (WCS). They also encounter offshore oil rigs, major shipping routes and potentially harmful toxicants.

The researchers used satellite tags affixed to more than a dozen whales to quantify the amount of overlap between hydrocarbon exploration and extraction, environmental toxicants, shipping lanes, and humpback whales occurring in their near-shore breeding areas. They were also able to identify additional parts of the whale’s breeding range and their migratory routes to sub-Antarctic feeding grounds. The study was published in the journal Conservation Biology.

“Throughout numerous coastal and offshore areas, important whale habitats and migration routes are increasingly overlapping with industrial development, a scenario we have quantified for the first time in the eastern South Atlantic,” said Dr. Howard Rosenbaum, Director of WCS’s Ocean Giants Program. “Studies such as this one are crucial for identifying important habitats for humpback whales and how to best protect these populations from potential impacts associated with hydrocarbon exploration and production, shipping, and other forms of coastal and offshore activities.”

Rosenbaum added, “From understanding which habitats are most important to tracking their migrations, our work provides great insights into the current issues confronting these whales and how to best engage ocean industries to better protect and ensure the recovery of these leviathans.”

Humpback whales reach nearly 50 feet in length and are characterized by their long pectoral fins, acrobatic behavior, and haunting songs. Commercial whaling fleets once hunted the humpback, like other great whales. Experts estimate that nearly 90 percent of the global population of humpbacks were lost to hunting. Humpback whales have been protected from hunting since 1968 by the International Whaling Commission.

In other ocean basins and regions, the migration patterns of humpbacks have been the subject of extensive study. So far, however, the migratory behaviors of humpbacks along the western African coast in the eastern South Atlantic are poorly described. The research team used satellite research tags on 15 whales off the coast of Gabon between August and September of 2002 to understand the movements of the whales in the Gulf of Guinea.

“This study demonstrates clearly that all of the countries on the west coast of Africa need to work together on a range-wide humpback whale conservation strategy and consider the possibility of creating a whale sanctuary,” said Professor Lee White, CBE, director of Gabon’s National Parks Agency. “Gabon supports the concept of a South Atlantic Whale Sanctuary and will continue to work with other nations in the region to this end.”

“This technology allows the science and conservation communities to discover detailed seasonal migration routes, timing and destinations, so we can characterize these important habitats and reduce potential impacts of human activities, even in the harshest possible marine environments,” said Dr. Bruce Mate, who pioneered the satellite-monitored radio tagging of large whales.

The research team’s primary goal was to understand the migratory routes used by the whales from the breeding areas off western Africa to areas where the whales likely feed in Antarctic or sub-Antarctic waters. They found that the tagged whales, as a group, traveled more than 25,193 miles. Each whale traveled an average of 1,936 miles, with the tags transmitting data for 104 days. Two of the whales traveled an astonishing 5,000-mile migration from near the equator to the edge of the sub-Antarctic ice shelf around Bouvet Island.

Several whales predictably remained in the offshore waters of Gabon or traveled south. The team — which included Howard Rosenbaum of the Wildlife Conservation Society and the American Museum of Natural History; Sara Maxwell of Stanford University; Francine Kershaw of Columbia University; and Bruce Mate of Oregon State University — was surprised to discover that nearly half the tagged group moved north into previously undocumented breeding grounds. The researchers also tried to understand the overlap between whale movements and human intrusions such as oil platforms and shipping lanes.

“Whales make some of the most fascinating migrations of any animals in the world,” said Dr. Sara Maxwell, a researcher affiliated with the Stanford Woods Institute for the Environment and a study co-author. “As part of this study, we uncovered previously unknown migration routes of some of the world’s largest whales, showing that even today we are still in an age of discovery for these ocean giants.”

Overall, the team found that the whales spent nearly 76 percent of their time within the Exclusive Economic Zones (defined as 200 nautical miles from the coast) of 13 different African countries, but mostly in the Exclusive Economic Zones (EEZs) of Cameroon, Gabon, Nigeria, and Angola. In contrast, whales traveling north from and remaining in the coastal waters of Gabon spent an estimated 41 percent of their time in the presence of oil and gas platforms.

“There are indications that oil production in these regions has and will increase in the coming years, so gaining a better understanding of the movements of whales and quantifying the degree of overlap with human activities will help assess the potential risks to this population, and help us to identify and implement the most effective mitigation strategies and conservation programs,” concluded Rosenbaum.